Really embarring question? Serious answers only please!?

I am 9 weeks 4 days pregnant with twins. For a week or two I have been getting pains in my rectum when I sit a certain way. Also, last night I was lying on my stomach and I got really sharp pains in the rectum but they instantly went away when I turned onto my side. Is this normal or could something be wrong? I go to the OB next Monday and I plan on asking then but I'm just curious. Sorry is this is weird but please share your experience if any! Thanks